Images on item pages not displaying correct size or as square thumbnail

I believe item pages should be showing square thumbnails on the item page. This is not working for me, and I’m not sure why:
Link to problem: https://blackrap.lakeforest.edu/items/show/6

Note that I have tried many different themes, and I’m having the same problem where the full size image is trying to display on the item page.

On the rhythm theme, I have made changes to the item show.php file, but not the other themes, so I don’t think that is the problem. On another site I created, the square thumbnail works:
http://protesthistory.lakeforest.edu/items/show/76

Thanks! I don’t mine editing css or php if needed, but I’m perplexed. I’ve got the box “use square thumbnail” checked in settings. I do have Derivative Images installed and have tried running that. I don’t have that plugin on the site where images are displaying properly. Thanks!

The thumbnail there is a square thumbnail, it’s just being stretched out by the CSS.

In particular, the issue seems to be coming from a style on the “Connected Carousel” plugin, which is setting all images to be maximum width.

Thank you! I went crazy installing plugins the other day to solve a problem, and connected carousel was the culprit! Thanks so much, looks better now. Anne